Immune Suppression Uncovers Endogenous Cytopathic Effects of the Hepatitis B Virus

Abstract

It is generally accepted that the host's immune response rather than the virus itself is causing the hepatocellular damage seen in acute and chronic hepatitis B virus (HBV) infections. However, in situations of severe immune suppression, chronic HBV patients may develop a considerable degree of liver disease. To examine whether HBV has direct cytopathic effects in severely immune compromised hosts, we have infected severe combined immune deficient mice (uPA-SCID), harboring human liver cells, with HBV. Serologic analysis of the plasma of HBV-infected animals revealed the presence of extremely high amounts of viral genomes and proteins. Histological analysis of the livers of uPA-SCID chimeras infected with HBV for more than 2 months showed that the majority of human hepatocytes had a ground-glass appearance, stained intensely for viral proteins, and showed signs of considerable damage and cell death. This histopathologic pattern closely resembles the picture observed in the livers of immunosuppressed HBV patients. These lesions were not observed in animals infected with HBV for less than 1 month. Ultrastructural analysis of long-term-infected hepatocytes showed a highly increased presence of cylindrical HBsAg structures, core particles, and Dane particles compared to short-term-infected hepatocytes. These long-term-infected hepatocytes also contained elevated amounts of HBV cccDNA. In conclusion, HBV causes dramatic intracellular changes and hepatocellular damage in the human hepatocytes that reside in a severely immune deficient mouse. These lesions show much resemblance to the ones encountered in immunosuppressed chronic HBV patients. Our observations indicate that HBV may be directly cytopathic in conditions of severe immune suppression.

In vivo proliferation of hepadnavirus-infected hepatocytes induces loss of covalently closed circular DNA in mice

“…WM-HBV-infected PTHs generated in uPA chimeric mice do not undergo hepatocellular changes, such as lipid droplet accumulation, nor do they show any sign of damage after longterm residence in immunosuppressive uPA mice, as has been reported for human hepatocytes. 21 Hence, tupaia chimeric mice were chosen for serial transplantation of hepadnavirus-infected primary hepatocytes. Because of the lack of centromere structures able to ensure migration of the nuclear cccDNA minichromosome during cell division, a random and possibly unequal distribution of the cccDNA pool can be expected.…”

Use of RNA interference to modulate liver adenoma development in a murine model transgenic for hepatitis B virus

“…Ultrastructural analysis revealed that the enlarged nuclei were filled with 20-22 nm nucleocapsid particles (Figure 2b, panel 2, inset), resembling those found in similar HBV transgenic or infected animal models and in chronic HBV patients. 15,16 Swollen hepatocytes with various sizes of cytoplasmic vacuolations (Figure 2b, panel 3) and features of individual hepatocyte coagulative necrosis (Figure 2b, panel 4) demonstrated degenerative changes. In contrast, the non-transgenic mice did not show overt hepatic lesions (Figure 2b, panel 1).…”

“…Our result is consistent with recent findings which demonstrate that HBV by itself can generate cytopathic effect in a human hepatocyte-transplanted immunodeficient mouse model, and, more importantly, that the severity of liver disease was positively correlated with the extent and duration of HBV infection. 16,26 The HBV-associated liver injury seen in the ICR/HBV model, similar to that in chronic HBV patients, takes a long time to establish, beginning at about 10 months of age then gradually becomes more severe. Compared with similar whole genome HBV transgenic mice, which do not develop liver injury, 15,[19][20][21]27 our ICR/HBV mice produced much higher levels of serum HBV for a much longer time (up to at least 2 years of age).…”

The regulation of proteins associated with the cytoskeleton by hepatitis B virus X protein during hepatocarcinogenesis

“…One important feature of the cytopathic effects (CPEs) mediated by viral infection is morphological changes in the host cells. Previous studies have demonstrated that HBV infection is able to induce CPEs in hepatocytes, with a ground glass appearance in the human liver/promoter-driven urokinase-type plasminogen activator/severe combined immunodeficiency mouse model or in cultured HeLa cells (19,20). Further studies reported that HBV-replicating HepG2 cells exhibited morphological changes and had the appearance of membrane rufflings and lamellipodia-like structures (21).…”